1. Field of the Invention
The present invention relates to a stair tread support and more particularly to a stair tread support for a spiral staircase in which a plurality of stair treads are spaced spirally and extend outwardly from a central support column. Even more particularly, the invention relates to hook and bracket means adapted to support the stair treads on the column.
2. Description of the Prior Art
Spiral staircases are common and a very diverse number of means are used to support spirally located stair treads on a central column from which the treads extend. It is common to fabricate spiral staircases which include a vertically oriented tubular metal column or pole. These tubular metal columns are provided in some instances with special slots which are engaged by bosses or pins attached to the inner end of a stair tread. The pins when engaged in the slots support the stair tread on the column. For example, U.S. Pat. No. 4,587,780 shows such a stair tread support system. U.S. Pat. No. 485,449 shows another form of spiral staircase in which stair treads are supported by studs which extend through slots or openings formed in a tubular metal column. In both of these patents the stair tread is supported in cantilever fashion from the central support column.
Numerous other forms of spiral staircase supports are known in the prior art. For example, a stair tread may be supported mortise like by a cantilever arm which extends through a slot formed through a center support pole; the stair treads may be supported by providing the stair tread with an integral wooden ring at its inner end. This wooden ring is assembled over an elongated steel rod with wooden collars placed between the rings to space the treads from one another. Other constructions have been provided which include means for mounting a wooden tread on a steel arm having a steel ring at its inner end. This steel ring is a substitute for the wooden ring noted above.
It is particularly desirable from an aesthetic standpoint to fabricate a spiral staircase where the resulting construction only includes finished wood for all of the exposed surfaces. This, of course, is not possible in those constructions where the center column is formed of a length of tubular metal. Further, in those systems where wooden collars are used to space the stair treads from one another, a number of parts are involved in constructing the staircase which, of course, is disadvantageous from the standpoint that a large number of parts are necessary to construct the staircase at site location. Also, where a staircase is constructed from a large number of parts, it is inherently less strong and involves a substantially greater number of assembly steps, particularly in precision placing or adjusting of the individual stair treads. On the other hand, it is desirable to employ the strength of steel in stair construction where possible without sacrificing aesthetic considerations.